1. Field of the Invention
This invention relates to light emitting semiconductor devices and processes, and more particularly to light emitting semiconductor devices and processes that use spin-polarized carriers to produce circularly polarized light.
2. Description of the Related Art
Circularly polarized light, especially modulated (i.e. pulsed) circularly polarized light, is useful in optical switching and optical computing applications.
It is known that a light emitting diode (LED) emits unpolarized light and that a quarter wave plate may be used to filter this light to produce circularly polarized light. However, attaching this additional component on or adjacent to an LED requires an additional manufacturing step, and increases the size of the component.
Skilled practitioners in the art will recognize that FIG. 1 shows a typical known LED structure 10 for producing unpolarized light. This LED structure 10 has at least one n-doped semiconductor layer 12 adjacent to at least one p-doped semiconductor layer 13 to form a p-n junction. This p-n junction is usually disposed on a semiconducting substrate 14. This structure is connected to a voltage source 16 through a pair of electrical contacts 11. Positioned in the path of light emitted from this structure is a quarter wave plate 15.
In operation, when a voltage is applied to this LED structure 10 through the contacts 11, electrons will be injected into the p-n junction from one direction, while holes will be injected into the p-n junction from the opposite direction. These electrons and holes will recombine or decay to produce unpolarized photons. When this unpolarized light passes through the quarter wave plate 15, it emerges as circularly polarized light.